Introduction: UPS for WiFi Router V4

Hi All,

With increased Work from home, we all want to work uninterrupted, power failure are very common in India.. Many apartments have installed backup generators, which kicks in within few seconds of power failure.

Even if the power failure is for few seconds, the router takes few minutes to reconnect. These router are powered at 5, 9 or 12V and with new trend, we have a 5V fiber converter. All of these are less than 30W and the regular UPS will switch off as 30W is not considered as load. There are DC Lithum battery UPS, but they give limited option, only one device can be connected. On Youtube, you may find that people use powerbanks to power a 5V Routers, while this will work for 5V router but not for 9 or 12V..

I have been making and using DC Lithium ion battery UPS for few years now. Based on requests from friends and family, I have been modifying these circuits to support different setup and I think after 3 years, I have all the combinations as below, depending on your power requirement you can choose which version you want to make...

  • Version 1 :Link (5W)
    • Single Output 9V and 0.5A
    • Can be modified to set output to 5V, but not 12V
  • Version 2:Link (15W)
    • Dual Output 9V/0.5A and 5V/1.5A
    • Can be modified to supply two 5V outputs
  • Version 3: Link (24W)
    • Single output 12V/2A
    • Can be modified to step-down to 5 or 9V
  • Version 4 (36W) - This Page
    • Dual Output 12V and 5V
    • Output can be modified to both 5V or 9V
    • Or Single output at 12V- I have attached circuit for this variant as part of this instructions

As in my previous UPS versions, I am using Lithium ion batteries extracted from old laptops.

In this project I am using an old pvc plastic tiffin box as enclosure, to increase reuse and reduce wastes

Step 1: What Do We Need?

  • Lithium Ion batteries
  • 3S BMS
  • SMPS 12V 3A
  • XL4015 : CC CV Step-down Buck Converter - Used to safely charge Lithium Ion batteries
  • LM2596 : Step down Buck converter - used for step down output Voltage
  • Wires
  • Old Tiffin box as enclosure
  • Soldering Iron

Step 2: 3S Battery Pack

  • Before we make the battery, pack, make sure all batteries are charged completely, I do this using TP4096 module...
  • Create a 3s battery pack, by connecting 3 Lithium ion battery in series
  • Mark +ve and -ve and place these in the most comfortable way to solder them together using thick copper wire
  • Solder the 3s battery pack to a BMS as shown
  • I use paper tape to hold batteries together

Step 3: Setting Up 5V Output

  • Solder the LM2596 to the battery pack
  • Adjust the variable resistor on the module in anticlock direction
  • Monitor the voltage drop using Multi meter and set output at 5V
  • Typically LM2596 can withstand 3A as output.
  • Try not to use any device above 2A

Step 4: Set XL4015 Outputs

  • We will use XL4015 OUtput voltage to 12.6V and Current at 2.3A
  • Refer the attached diagram to adjust the V and I to desired value
  • This module can withstand upto 5A
  • If you need higher Amp output both SMPS and XL4015 needs to be changed to suitable modules

Step 5: Assembly

  • Place all components in a enclosure of your choice and make sure that they do not touch each other
  • I would advice not to use metal cases, but you use them, then please make sure to insulate all circuits and wire carefully to avoid any short circuit
  • Before hot glue-ing each part, make sure all needed wire are properly connected to their respective modules
  • Refer the circuit diagram for connect details
  • I added few holes on the lid of the tiffin box for any heat dissipation

Step 6: Variants 12V 2A or Higher

Based on comments received on my V3 design, I could guess that many people have 12V routers.

  • Single Device with Output 12V uptill 2a ( Less than 24W)
    • Use the circuit attached
    • We do not need to step-down output voltage
  • Dual Devices at 12V and current requirement less than 4A ( less than 40W)
    • Use same circuit design, but
    • Change SMPS to 12V 5A
    • Set current on XL4015 to 4A
    • The Lithum Ion cells from laptops can support easily 4A in 3S config for few hours
  • Beyond 40 Watts
    • make multiple UPS
  • Beyond 100W
    • Use regular UPS